Question

The coordination number of a central metal atom in a complex is determined by ________.
A) The number of ligands around a metal ion bounded by sigma bonds.
B) The number of ligands around a metal ion bounded by pi-bonds.
C) The number of ligands around a metal ion bounded by sigma and pi-bonds.
D) The number of only anionic ligands bonded to the metal ion.

Answer 1

The answer for this question can be approached by knowing the definition of coordination compounds which is the basic concept of the coordination chemistry.

Complete Solution :
In the lower classes of chemistry, we have studied the basic concepts in inorganic chemistry that deals with the chapter called coordination chemistry.
- Now, we shall study this in detail so that we can know the exact answer to be arrived at for the given question.
- Coordination chemistry simply deals with the coordination complexes that are formed which consists of a central metal atom or ion which is usually metallic in nature and this will be the coordination centre and then surrounding array of bound molecules or ions which are known as ligands.
- Thus, coordination number which is also called as ligancy of central metal in the molecule is the total number of atoms, molecules or ions that are bound to it.
- Coordinate bonds are also called as coordinate covalent bonds or dative bonds and can be defined as number of sigma bonds attached between the ligands and central metal atom or also defined as number of ligand donor atoms attached directly to the central atom.
- Thus, coordination requires a sigma bond to be present and pi bond does not contribute to this.
So, the correct answer is “Option A”.

Note: Note that the ligands in the coordination complexes are also called as complexing agents and the name is because it complexes with the metal ions to form a chelate rings or also other complexes and this property is useful in many applications which includes its use as cleansing agents and also some are used in textile processing.